In processes using aqueous solutions, corrosion of metal surfaces may occur at various locations including feed lines, heaters, steam lines, process tanks and return lines. The presence of dissolved gases such as carbon dioxide and oxygen in the water can be a principal factor influencing this corrosion, particularly where iron and steel are materials of construction.
In boilers, carbonate or bicarbonate compounds are frequently added to make the feedwater alkaline. The materials can decompose at boiler operating conditions to produce carbon dioxide with the steam such that there is increased corrosion of steam lines and steam condensate return lines. Neutralizing amines react with carbon dioxide in the condensate and are well known in the boiler water condensate art as additives customarily used to reduce corrosion due to carbon dioxide. See e.g. H. H. Uhlig, et al. "Corrosion and Corrosion Control," page 291, John Wiley & Sons, Inc. (1985). The corrosion of the iron and steel pipes, boilers, and economizers of conventional boiler systems in oxygenated conditions is also a well known problem; and controlling the presence of oxygen in boiler systems, particularly in the feed water section, has received considerable attention. Oxygen removal may be partially accomplished by either vacuum or thermal deaeration, or both. Complete removal of oxygen cannot be effected by these means, however, and further removal by use of a chemical scavenging agent, such as sodium sulfite, is a well-known practice.
In recent times, the use of low pressure boilers (operating below about 150 psig) has been increasingly supplemented by use of boilers operating at moderate pressure (operating between about 150 psig and about 600 psig) and high pressure (operating above about 600 psig). As boiler operating temperatures and pressures have increased there has been particular interest in the performance of oxygen scavengers at these operating conditions. For example, use of sulphites at elevated temperatures and pressures may cause an increase in solids, and formation of sulfur dioxide and hydrogen sulfide, both of which can be a source of corrosion. Scavengers such as hydrazine, hydroquinone, and certain hydroxylamines have been found to perform satisfactorily in some circumstances. In other circumstances, the efficiency with which the scavenging proceeds has not been optimal. There is thus a continuing need for alternative oxygen scavengers which can be effectively used at elevated temperatures and pressures.
Despite the toxicity of hydrazine, much recent research has concerned development of corrosion inhibitors using hydrazine together with various organic products. U.S. Pat. No. 3,551,349 to Kallfass suggests using hydrazines in combination with activating amounts of various quinone compounds (including hydroxyl forms such as pyrocatechol and hydroquinone) and their derivatives, particularly those with hydrophilic substituents such as carboxylic acid and sulphonic acid. U.S. Pat. No. 3,843,547 to Kaufman et al. discloses a hydrazine-hydroxyl quinone combination in further combination with various aryl amine compounds. U.S. Pat. Nos. 4,026,664 and 4,079,018 to Noack disclose hydrazine-based corrosion inhibitors which use organometallic complexes (including those of sulfonated pyrocatechol and certain amino derivatives of carboxylic acids) as catalysts, and preferably, quinone compounds (including hydroquinone) and their derivatives (including sulfonic acid derivatives) to render the compositions compatible with phosphonate scale control agents.
Other work has focused on hydroxylamines. U.S. Pat. No. 4,067,690 of Cuisia et al. discloses that hydroxylamine and certain derivatives thereof are highly effective oxygen scavengers in boiler water. The hydroxylamines may be catalyzed with any of a number of well-known catalysts used in sodium sulfite or hydrazine boiler water treatment. Alkali metal hydroxide, water soluble metal salts, hydroquinone, and benzoquinone are also useful catalysts. As disclosed in U.S. Pat. No. 4,350,606 to Cuisia et al., the use of a hydroxylamine compound and a volatile, neutralizing amine such as cyclohexylamine, morpholine, diethylaminoethanol, dimethylpropanolamine, or 2-amino-2-methyl-1-propanol, inhibits corrosion in boiler systems caused by carbon dioxide and oxygen. Japanese Patent Document SHO 57-204288 to Sato discloses using certain hydroxylamines as de-oxidants in combination with certain trivalent phenols, napthoquinones, and anthraquinones or derivatives thereof (such as sodium 1,2 napthoquinone-4-sulfonate), as activating agents. The invention may be practiced in boiler related systems and activity is deemed particularly significant in neutral and alkaline pH ranges. U.K. Patent Application No. GB 2,157,670A by Nemes et al. reveals advantageous use of hydroxylamines together with neutralizing amines and a quinone, a dihydroxybenzene, a diaminobenzene, or an aminohydroxybenzene compound to scavenge oxygen and to inhibit corrosion in boiler water and other aqueous systems. The "quinone-benzene" component may comprise various sulphonated napthalenes.
Hydroquinone and some related compounds have also been used in corrosion inhibition. U.S. Pat. No. 4,278,635 to Kerst discloses use of various dihydroxy, diamino, and amino hydroxy benzenes and their lower alkyl substituted derivatives (including sulfonated napthalenes), and particularly hydroquinone, as deoxygenating corrosion control agents which compare favorably with other scavengers such as hydrazine. Reaction rate increases with higher pH and higher temperature are disclosed, as is use of the invention in boiler systems. U.S. Pat. Nos. 4,279,767 and 4,289,645 both to Muccitelli are directed to use of hydroquinone as an oxygen scavenger in combination with various compatible amines. Addition of hydroquinone to boiler feedwater together with certain neutralizing amines used to neutralize carbon dioxide in the boiler condensate system is disclosed. The systems preferably have elevated temperatures and/or alkaline conditions. U.S. Pat. No. 4,282,111 to Cuiba also relates to a method of reducing oxygen in aqueous, preferably alkaline medium, including boiler system water, using hydroquinone. Hydroquinone is shown to perform equal to or superior to hydrazine under various conditions. Kaufman and U.S. Pat. No. 4,363,734 to Slovinsky claim use of hydroquinone as a catalyst in combination with other oxygen scavengers, namely hydrazine and dihydroxy acetone, respectively. U.S. Pat. No. 3,764,548 to Redmore discloses an oxygen scavenging system using an anthraquinone disulfonic acid compound and a vanadate salt to catalyze reducing agents such as hydrogen sulfide or hydrazine. Japanese Patent Publication No. SHO 51-93741 by Sozuki et al. reports synergistic inhibition of metallic corrosion by combinations of dihydroxy-benzenes (e.g. hydroquinone and methyl hydroquinone) and various carboxylic acids. Boiler water use is suggested. European Patent Publication No. 0039130 is directed to use of certain "dioxo" aromatic compounds (e.g. hydroquinone, benzoquinone, napthoquinone, catechol), including certain organically substituted derivatives thereof, as oxygen scavengers in aqueous medium, including boiler water. The "dioxo" scavengers are deemed to outperform hydrazine under certain conditions and are preferably used in alkaline pH.
European Patent Publication No. 0054345 is directed to use of certain aminophenol compounds to reduce oxygen in aqueous medium such as boiler water. These scavengers are deemed to outperform hydrazine in simulated feedwater conditions and are preferably used in alkaline pH.
Quinones, and substituted aromatics have found application in various arts. For example, U.S. Pat. No. 2,835,715 to Tiede identifies oxygen absorbing agents for certain process streams, including resorcinol, pyrogallol, phloroglucinol, quinone, hydroquinone, chlorohydroquinone, and tertiarybutylcatechol. Swedish Specification No. 308,974 discusses the use of sulfonated benzenes, hydroxy benzenes, naphthalenes, and related compounds in combination with phosphoric acid and amino acid for pickling and phosphatizing baths. U.S. Pat. No. 2,170,596 to Quiggle describes oxygen-absorbing solutions using catalysts such as various quinones (including sodium anthraquinone beta sulfonate and hydroquinone) together with reducing agents such as sulfides. Soviet Patent Publication No. 296,449 discloses use of sodium anthraquinone-2-sulfonic acid to protect titanium from acid corrosion. U.S. Pat. No. 2,682,563 to Bell et al. discusses use of propenyl derivatives of hydroquinone as antioxidants particularly valuable in protecting fats and oils. Synergists, including phosphoric acid and amino acids, are disclosed.
Hydroquinone-2-sulfonates are known chemicals, and have been used in diverse applications, including as a component of certain liquid membrane processes for removing uranium ions or the like from a fluid (see for example U.S. Pat. No. 4,337,225); as a reducing agent for preparing heat developable film (see for example U.S. Pat. No. 4,504,575); and as an agent for treating heart disease (see for example U.S. Pat. No. 4,513,007).